A group campaigning against the proposed NHS reforms, and inspired by UK Uncut's tactics, has staged its first protest.

NHS Direct Action targeted private health firm Care UK's offices, close to Liverpool St station in London, on Monday. About 50 people took part – a mixture of student doctors, workers and former NHS staff.

Toby Simmons, a medical student at UCL, representing the campaigners, said: "Having been involved in the student movement over the last five or six months and as a medical student it seemed logical to funnel some of that energy toward challenging the health and social care bill. We're taking UK Uncut's idea of a simple message linked with a viable alternative.

"UK Uncut changed the rules by showing that spaces – even inside shops – are perfectly legitimate places to protest. It's harder to use the same methods with the private health firms that are circling the NHS – they don't have the same high-profile public image as Topshop or Vodafone – but we're attempting to show that the NHS is for everyone rather than for the elite few to make a profit from."

The group says it has targeted Care UK because the firm is set to be one of the biggest beneficiaries of the health and social care bill. They say that Caroline Nash, wife of John Nash, the then chairman of Care UK, gave a personal donation of £21,000 to Andrew Lansley, to fund his office when he was shadow health secretary.

"I work for a large voluntary sector organisation, where we've already been hit hard by the cuts," said a supporter, who asked for her name to be withheld. "I'm really worried about what will happen to the NHS if this bill goes through. If we don't act then we're going to see everything we care about in this country destroyed."

Eileen Smith, 78, said she had been in the NHS, as a nurse and midwife, all her working life. "I feel passionately about it. I joined in 1948 when Aneurin Bevan created the NHS. It was a time when the country was on its knees. We were so proud that we had created something like this. It wasn't for profit. Everyone was going to have this equal, universal service. I still have the same passion for it.

"Now what's happening is private companies are picking off the easy parts, making a profit out of it. If we're not careful we'll end up with a US-style service."